This epidemiological study will prospectively examine the 17-year patterns of morbidity, mortality, functional ability, and health services utilization in a random sample of adults over 38 years old in 1965 in Alameda County, California, who have been followed by the Human Population Laboratory. These 4,131 non-institutionalized adults were first interviewed in 1965 (1,743 55 years or older); survivors were reinterviewed in 1974 (1,843 55 years or older), and 50% of those survivors were interviewed for a third time in 1982-83 (984 over 55 years or older). In addition, the mortality experience of this cohort has been followed and will be ascertained through 1983. This data base will allow us to examine a variety of factors which have been implicated in the epidemiology of aging. Information is available on discretionary health practices (smoking, alcohol consumption, relative weight, sleep habits, physical activity, and eating practices), social and psychological functioning, and life events such as retirement and bereavement. Analyses will permit us to investigate how these factors, independently and in combination, are associated with four measures of health status in an aging group which has been followed for over 17 years. Findings will permit us to specify those epidemiological factors which are associated with maintenance of good health and functioning in the aged.